Since approximately 100 years ago, when first technologies for wireless data transmission began to be employed, the bandwidth available for transmission has grown continuously. In order to be able to satisfy the continually increasing demand, waves in the terahertz range will be used in the future as carriers with especially high carrier frequencies in order to achieve data transmission rates in the range of 10 Gbit/s and higher with these waves.
Such terahertz waves can be generated by means of ultrafast electronic circuits or by means of optical methods. Since the electronic methods are limited in their speed on account of the lifetimes of free electrons and holes, however, these methods operate only inefficiently, if at all, at frequencies above 100 GHz. In contrast, the prior art optical methods for generating terahertz waves mostly employ higher frequencies that are then reduced by frequency mixing. Thus, in the meantime methods have become known with which terahertz waves are generated with high efficiency by difference frequency generation of two light waves in the infrared, visible, or ultraviolet spectral range.
At the present time, however, it is still relatively difficult to control the propagation of terahertz waves. The mirrors and lenses required for control are highly complex and can only be produced at correspondingly high expense if they are to be electronically controllable.